I have a shaded corner behind a Chinese Red Birch tree. It is empty, and all I see is the ugly side of my neighbour's outbuilding. I really want to cover that up, with something that doesn't take up a lot of space, yet is tall. I have a bench there, it's a lovely place to sit, but the building spoils it. What can I plant there, that is tall, fairly fast growing, likes shade and looks pretty without taking up a lot of space?